Image sensor, position sensor device, lithography system, and method for operating an image sensor

ABSTRACT

An image sensor for a position sensor apparatus for ascertaining a position of at least one mirror of a lithography apparatus includes: a plurality of integrated optical waveguides; a plurality of incoupling areas; a multiplexer apparatus; and an image reconstruction apparatus.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of, and claims benefit under35 U.S.C. § 120 to, international application PCT/EP2019/053298, filedFeb. 11, 2019, which claims benefit under 35 USC 119 of GermanApplication No. 10 2018 202 096.5, filed Feb. 12, 2018. The entiredisclosure of each of these applications is incorporated by referenceherein.

FIELD

The present disclosure relates to an image sensor for a position sensorapparatus, a position sensor apparatus including such an image sensor, alithography apparatus including such a position sensor apparatus, and amethod for operating such an image sensor, such a position sensorapparatus, and/or such a lithography apparatus.

BACKGROUND

By way of example, lithography apparatuses are used in the production ofintegrated circuits or ICs for imaging a mask pattern in a mask onto asubstrate such as e.g. a silicon wafer. In so doing, a light beamgenerated by an optical system is directed through the mask onto thesubstrate.

In this case, the representable structure dimension can depend greatlyon the light wavelength used. In order to attain particularly smallstructures, it is often desirable to use radiation of particularly shortwavelength. EUV lithography apparatuses use light having a wavelength inthe range of 5 nm to 30 nm, in particular 13.5 nm. “EUV” denotes“extreme ultraviolet”. In the case of such lithography apparatuses,owing to the high absorption of light of this wavelength by mostmaterials, reflective optical units, that is to say mirrors, are usuallyused instead of refractive optical units, that is to say lens elements.Moreover, in general, the housing in which the imaging optical unit issituated is evacuated because even the presence of a gas can result ingreat absorption of the radiation.

The mirrors may be secured to a force frame, for example, and may beconfigured to be at least partially manipulable or tiltable in order toallow a movement of a respective mirror in up to six degrees of freedom,and consequently a highly accurate positioning of the mirrors inrelation to one another, in particular in the pm range. This can allowchanges in the optical properties that occur for instance during theoperation of the lithography apparatus, for example as a result ofthermal influences, to be corrected.

For the purposes of aligning the mirrors, such as in the six degrees offreedom, actuators which are driven by way of a control loop can beassigned to the mirrors. An apparatus for monitoring the tilt angle of arespective mirror, for example, can be provided as part of the controlloop.

Document DE 10 2015 209 259 A1 describes a position sensor apparatus, inwhich an image sensor captures a pattern coupled to a mirror. There is aknown relationship between the image of the pattern on the image sensorand a deflection of the mirror from a rest position. Consequently, theposition of the mirror relative to the rest position can be deduced fromthe image recorded by the image sensor.

SUMMARY

Cooling the system can present a technical problem, particularly in thecase of evacuated exposure systems, because there may be no heattransfer medium in the space between the individual components.Therefore, designing used components in such a way that these generateas little heat as possible during operation can be desirable.

The present disclosure seeks to provide an improved image sensor.

According to a first aspect, an image sensor for a position sensorapparatus for ascertaining a position of at least one mirror of alithography apparatus is proposed. The image sensor includes a pluralityN1 of integrated optical waveguides and a plurality N2 of incouplingareas, with N2≥N1, each of the N2 incoupling areas being assigned to oneof the N1 integrated optical waveguides and configured to coupleincident light into the assigned integrated optical waveguide in such away that a light signal is generated in the assigned integrated opticalwaveguide. Furthermore, the image sensor includes a multiplexerapparatus, coupled to the N1 integrated optical waveguides, formultiplexing the light signals generated in the N1 integrated opticalwaveguides to a number N3 of secondary optical waveguides, with N1≥N3,and an image reconstruction apparatus, coupled to the N3 secondaryoptical waveguides, for reconstructing an image on the basis of thelight signals of the N3 secondary optical waveguides.

The image sensor can be considered as divided into three modules: Aninternal group, also referred to as a sensor front end, a signalconnection, and an external group. The internal group is arranged at thelocation where an image should be captured, for example in an evacuatedhousing of a projection optical unit of an EUV lithography apparatus.The external group can be flexibly arranged at another location, forexample outside of the housing of the projection optical unit. Thesignal connection transfers signals, for example optical and/orelectrical signals, between the internal group and the external group.

In some embodiments, the image sensor can provide the advantage of beingable to use a reduced number of electronic components for the purposesof capturing an image at the location of a sensor surface of the imagesensor. For example, the image reconstruction apparatus can be arrangedat a location distant from the sensor front end, for example outside ofan evacuated projection optical unit of a lithography apparatus.Consequently, the light signals are not already converted into anelectronically processable signal, in particular as a digital image, onor directly at the sensor surface, as would be the case for CCD or CMOSsensors, for example, but only in the image reconstruction apparatusarranged elsewhere. As a result, less thermal energy may arise in thesensor front end in comparison with purely electronic image sensors.

The sensor front end can include a substrate. For example, the lattercan be embodied as an integrated optical image sensor and having atleast the N1 integrated optical waveguides and the N2 incoupling areas.It can also be referred to as a chip or microchip. The integratedoptical image sensor can also be referred to as a photonic image sensor.For example, the image sensor for capturing the image includes a chipmanufactured in integrated fashion, the chip having, e.g., a layerstructure in which the plurality N1 of integrated optical waveguides andthe plurality N2 of incoupling areas are integrated. Consideredsubstrate materials for the chip include, in particular, silicon,silicon oxide, silicon carbide, group III-V semiconductor materials,such as, e.g., indium phosphide, and different glasses such as fusedquartz. To produce the integrated optical structures, for example theoptical waveguides, use can be made of methods known from microchipmanufacturing, in particular various coating and/or patterning methods.By way of example, an integrated optical chip thus manufactured has astructure dimension of less than 10 μm and is configured, for example,to transmit input coupled light substantially without losses.

To couple light into the N1 integrated optical waveguides, provision canbe made of N2 incoupling areas. An incoupling area can be assigned to arespective integrated optical waveguide. Here, a plurality of incouplingareas could be assigned to the same integrated optical waveguide. Forexample, the incoupling area is arranged at the start of the integratedoptical waveguide to which it is assigned. The start is understood tomean, in particular, an end of the integrated optical waveguide arrangedat the surface of the integrated optical image sensor. By way ofexample, the incoupling area can be considered to be the start of theintegrated optical waveguide. For example, the incoupling area can havecoatings, such as color filters, Bragg filters, antireflection coatings,etc., and/or be patterned. By way of example, each incoupling area is anarea at least partly transparent from an optical point of view. The sideof the incoupling area facing the integrated optical waveguide isreferred to, for example, as input coupling side or else back side. Theside facing the space in front of the integrated optical image sensor isreferred to, for example, as surface of the incoupling area.

If a light beam is radiated or incident on the surface of the incouplingarea, at least part of the light beam can be coupled into the integratedoptical waveguide and hence a light signal is generated in theintegrated optical waveguide. For example, the generated light signalmay be understood to mean the input coupled part of the incident lightbeam rather than a light signal newly generated by a light source. Inparticular, the generated light signal can depend on properties of thelight beam and on properties of the incoupling area. In particular,information transported by the incident light beam can also betransferred into the light signal. Further, a color-filtered lightsignal and/or polarized light signal can be generated by an appropriateembodiment of the incoupling area, for example, in particular withoutthe information transported originally by the light beam being lost.

A multiplexer apparatus can be coupled to the other end of the N1integrated optical waveguides. In particular, the multiplexer apparatuscan be embodied as an active integrated optical component. Themultiplexer apparatus can be integrated on the same chip as the N2incoupling areas and the N1 integrated optical waveguides.Alternatively, the multiplexer apparatus can be integrated on one ormore further chips. The multiplexer apparatus can be configured tomultiplex the light signals, supplied by the N1 integrated opticalwaveguides, to a number N3 of secondary optical waveguides. To this end,the multiplexer apparatus can include, for example, a number ofswitchable integrated optical structures. The switchable integratedoptical structures can be embodied, for example, as acousto-optic and/orelectro-optic components. Here, the switchable integrated opticalstructures can be drivable and/or switchable via an integratedelectronic circuit, in particular. Depending on a switching position ofa respective switchable integrated optical structure, the light signalcan be switched or multiplexed from one of the N1 integrated opticalwaveguides to one of the N3 secondary optical waveguides. In theprocess, the light signal can be coupled into the respective secondaryoptical waveguide, as a result of which a corresponding light signal isgenerated in the latter.

For example, the N3 secondary optical waveguides may not integratedoptical waveguides but are embodied, for example, as optical fibers.Therefore, the N3 secondary optical waveguides may be configured totransfer the light signals along almost any path. In particular, dampingof the input coupled light signals in the N3 secondary opticalwaveguides can be low, and so the N3 secondary optical waveguides canhave a length in the range of several meters, for example up to 10 m orelse up to 50 m, but the light signals may still able to be captured.

The N3 secondary optical waveguides can be configured to guide the inputcoupled light signals to the image reconstruction apparatus. The imagereconstruction apparatus can be configured, for example, to capture thelight signals from the N3 secondary optical waveguides and reconstructan image on the basis of the captured light signals. In particular, theimage reconstruction apparatus can include a number of electroniccomponents, such as one or more photodiodes for capturing and convertingthe light signals into electronic signals, an analog-to-digitalconverter (A/D converter), and/or an image processor. To capture thelight signals, the ends of the N3 secondary optical waveguides facingthe image reconstruction apparatus can be arranged so that the lightsignals are able to emerge from the N3 secondary optical waveguides andbe incident on the photodiode. In addition or as an alternative to thephotodiode, provision can also be made of a CCD sensor, a CMOS sensor,and/or a photomultiplier. By way of example, the electrical signalgenerated by the photodiode on the basis of the light signals can beconverted into a digital signal by an A/D converter, the digital signalbeing processable by a digital electronic circuit such as the imageprocessor or a CPU. The image processor can be implemented in terms ofhardware and/or else in terms of software. In the case of animplementation in terms of hardware, the image processor can be embodiedas a computer or as a microprocessor, for example. In the case of animplementation in terms of software, the image processor can be embodiedas a computer program product, as a function, as a routine, as part of aprogram code or as an executable object.

The image reconstructed in this way by the image reconstructionapparatus can have N2 pixels, for example, each pixel of thereconstructed image having an information item correlated with the lightincident on the respective one of the N2 incoupling areas.

In particular, the light signals can be captured in such a way that aunique assignment of a respective captured light signal to one of the N2incoupling areas is ensured. To this end, a synchronization device, forexample, which can for example be part of the image processor, canprovide a synchronization signal or else a trigger signal. By way ofexample, this synchronization signal can be used to drive themultiplexer apparatus and the A/D converter. To which of the N1integrated optical waveguides a light signal captured and digitized at acertain time may be assigned can therefore be ascertained taking accountof a signal propagation time, for example. Should light signals ofdifferent incoupling areas be frequency encoded, for example, this canbe taken into account accordingly when capturing the light signals, forexample by a color filter wheel.

Below, an example describes the operating principle of the image sensor.By way of example, the integrated optical image sensor has a pluralityN2=16 incoupling areas, which are arranged in a matrix of four columnsand four rows. This could also be referred to as a 4×4 array. By way ofexample, the integrated optical image sensor has a plurality N1=16integrated optical waveguides. Exactly one of the 16 incoupling areas isassigned to each of the 16 integrated optical waveguides. By way ofexample, the multiplexer apparatus has four switchable integratedoptical structures, which each multiplex four inputs to one output, oneof the integrated optical structures respectively being assigned to arow of the integrated optical image sensor. This could also be referredto as a 16×4 multiplexer. The four integrated optical waveguides of onerow are fed to the four inputs of the switchable integrated opticalstructure assigned to this row, the switchable integrated opticalstructure having a secondary optical waveguide coupled to the outputthereof. Thus, a total of four secondary optical waveguides are providedin this example, each coupling to one of the switchable integratedoptical structures of the multiplexer apparatus. The four secondaryoptical waveguides guide light signals coupled therein to a respectivephotodiode of the image reconstruction apparatus, the latter thereforehaving four individual photodiodes. The synchronization device clocks,for example, the four switchable integrated optical structures of themultiplexer apparatus in such a way that, over a certain time interval,for example the light signals of the incoupling areas forming the firstcolumn are coupled into the secondary optical waveguides and captured bythe respective photodiode. In a next time interval, there is, forexample, a switch such that then the light signals of the second columnare captured, etc. Overall, this allows an image information item, forexample a pattern present on the sensor surface of the integratedoptical image sensor with the N2 incoupling areas, to be captured.Without loss of generality, N1=16, N2=16, N3=4, and four photodiodeswere chosen in the preceding example.

According to some embodiments of the image sensor, the plurality N2 ofincoupling areas, the plurality N1 of integrated optical waveguides andthe multiplexer apparatus are integrated on a substrate, in particularon an integral substrate.

Consequently, the integrated optical image sensor can be formed on asingle microchip using known manufacturing methods. In particular, themicrochip can have both integrated optical structures and integratedelectronic structures. By way of example, the integrated optical imagesensor can have contact points for driving the multiplexer apparatus,which contact points can be attached to the front side of the microchipand/or to the back side of the microchip. In particular, thesynchronization signal and/or further control signals for themultiplexer apparatus can be transferred to the microchip via thesecontact points.

An integral substrate is understood to mean, in particular, that thesubstrate for the entire integrated optical image sensor has beenproduced from the same original wafer and has not been joined together.This could also be referred to as a monolithically integrated circuit.

According to some embodiments of the image sensor, the multiplexerapparatus is configured to multiplex the light signals via atime-division multiplexing method, a frequency-division multiplexingmethod, and/or a code-division multiplexing method.

In a time-division multiplexing method, different signals are separatedfrom one another in time. In a frequency-division multiplexing method,different signals are transferred simultaneously at differentfrequencies. By way of example, such signals can be generated usingcolor filters and can also be separated by color filters again. In acode-division multiplexing method, a plurality of different signals aretransferred simultaneously in encoded fashion and with different codesequences, for example spreading code sequences. In particular, thedifferent signals can correspond to different light signals, generatedby the N2 incoupling areas, in the N1 integrated optical waveguides.

By way of example, the time-division multiplexing method can be used ifN1=N2. Should N1<N2, a frequency-division multiplexing method, forexample, is suitable for discriminating the light signals generated in arespective integrated optical waveguide by different incoupling areas.By way of example, the surfaces of the N2 incoupling areas havedifferent color filters to this end.

According to some embodiments of the image sensor, the imagereconstruction apparatus includes a capturing device for capturing thelight signals of the N3 secondary optical waveguides and asynchronization device. The synchronization device can be configured todrive the multiplexer apparatus via a synchronization signal in such away that a respective light signal captured by the capturing device isuniquely assignable to an incoupling area of the plurality N2 ofincoupling areas of the image sensor.

In particular, the capturing device can include one or more photodiodes,a CCD sensor, a CMOS sensor, and/or a photomultiplier. In particular,the synchronization device can include a clock, which provides a clocksignal at a known and constant frequency.

According to a further embodiment of the image sensor, the surface of arespective incoupling area of the plurality N2 of incoupling areas has apredetermined angle with respect to the incident light.

This could also be referred to as the incoupling angle or an angle ofincidence. In order to obtain efficient input coupling, it may beadvantageous not to align the surface orthogonal to the incident lightsince an integrated optical waveguide can only transport certain modes,for example material-dependent and structure size-dependent modes. Thesemodes can be excited by light with certain wave vectors.

Here, the wavelength or the frequency of the incident light could alsobe taken into account.

In particular, the angle of the surface of two incoupling areas couldalso be different, for example because the respective incoupling areashave different filters.

According to some embodiments of the image sensor, the latter includesan imaging unit for imaging a pattern of a pattern provision device, tobe captured by the image sensor, on the plurality N2 of incoupling areasof the image sensor.

By way of example, the imaging unit includes one or more lens elements.In particular, the imaging unit could also include a micro-optical unit,in which one or more lens elements are provided for each N2 incouplingarea of the integrated optical image sensor.

In particular, the imaging unit can be configured to generate at thelocation of the sensor surface of the integrated optical image sensor animage of the pattern to be captured. Further, an advantage of theimaging unit, in particular, can be that it can cause an increase in theluminous power incident on a respective incoupling area. This can,firstly, improve a signal-to-noise ratio and, secondly, reduce a usedillumination light power, which allows a reduction in an energy influx,for example into an evacuated projection system of a lithographyapparatus.

The imaging unit may also be suitable for imaging a pattern which doesnot lie in a plane but is curved. Further, the imaging unit could beembodied in such a way that the imaging of the pattern is implemented inan oblique plane in relation to a line of sight from the sensor surfaceto the pattern provision device.

By way of example, the pattern provision device has a pattern with aninformation content at spatial frequencies of at least 1/(500 μm).

According to some embodiments of the image sensor, a number N4 ofsecondary integrated optical waveguides and a number N5 of outcouplingareas, with N5≥N4, are provided. Each of the N5 outcoupling areas can beassigned to one of the N4 secondary integrated optical waveguides andconfigured to output couple from the assigned secondary integratedoptical waveguide a light signal, generated in the assigned secondaryintegrated optical waveguide, for illuminating the pattern to becaptured by the image sensor.

The number N4 of secondary integrated optical waveguides and the numberN5 of outcoupling areas can be integrated, for example, on a dedicatedsubstrate or, as an alternative thereto, on the same substrate, inparticular on the integrated optical image sensor or chip. The number N4of secondary integrated optical waveguides and the number N5 ofoutcoupling areas together can form, for example, an illuminationarrangement. A light signal, generated in the N4 secondary integratedoptical waveguides, can be guided to the N5 outcoupling areas and isoutput coupled or emitted there, at least in part, from the respectivesecondary integrated optical waveguide. Different outcoupling areas,like incoupling areas, may have different properties in order to obtainan advantageous emission behavior. In particular, optical gratings maybe provided on a respective outcoupling area in order to achieve adirection-dependent emission.

According to some embodiments of the image sensor, the latter caninclude an illumination device for generating a light signal in anillumination optical waveguide. Coupled to the illumination opticalwaveguide may be a distribution apparatus, which is configured todistribute the light signal, generated in the illumination opticalwaveguide, to the number N4 of secondary integrated optical waveguides.

The illumination device can include one or more illuminants or lightsources, for example lasers, gas discharge lamps, incandescent lamps,light-emitting diodes and/or arc lamps. The illumination device can beconfigured to provide a predetermined light spectrum. In particular,broadband or monochromatic light may be provided. In some embodiments,it may be advantageous for the wavelength of the light to lie in a rangebetween 100 nm and 10 μm.

By way of example, an illumination optical waveguide is embodied as aglass fiber. Hence, the illumination optical waveguide can be configuredto transport the light signal generated therein over a relatively largedistance, such as 10 m or 50 m, for example. Consequently, theillumination device can be arranged at a distance from the locationwhere the light generated by the illumination device should be used forillumination purposes. In particular, the illumination device can alsobe efficiently cooled using a simple technical approach as a resultthereof.

The illumination optical waveguide or waveguides can be coupled to thedistribution device. By way of example, the distribution device is apassive integrated optical circuit, which is arranged on the chip onwhich the N4 secondary integrated optical waveguides are integrated. Thedistribution device could also be referred to as a splitter. Thedistribution device can distribute the light signal supplied by theillumination optical waveguide or waveguides among the N4 secondaryintegrated optical waveguides, which guide the light signal to the N5outcoupling areas.

This arrangement can allow the pattern to be captured to be illuminatedin advantageous fashion, without waste heat of a light source arising inthe region where the illumination is used.

According to some embodiments of the image sensor, the number N4 ofsecondary integrated optical waveguides and the number N5 of outcouplingareas and/or the distribution apparatus can be integrated on thesubstrate.

Particularly advantageously, both the image capture and the illuminationcan consequently be arranged on a single integrated optical substrate.

According to a further embodiment of the image sensor, 16≤N2≤16384, forexample, 256≤N2≤4096 applies.

The plurality N2 of incoupling areas can set the number of pixels in thereconstructed image. In particular, each pixel in the reconstructedimage can correspond to exactly one incoupling area.

According to some embodiments of the image sensor, a structure dimensionof the N1 integrated optical waveguides and/or of the N4 secondaryintegrated optical waveguides is less than 1 μm, such as less than 500nm, for example, less than 150 nm.

The smaller the structure dimension of the integrated optical waveguide,the higher integration density can be. A substrate area can be used moreefficiently with a higher integration density, allowing production coststo be lowered. Further, an increased resolution can improve the qualityof the image capture by the image sensor.

According to some embodiments of the image sensor, an edge length of apixel of the image sensor can lie in the range between 5 μm and 500 μm,in particular between 40 μm and 160 μm.

In relation to the sensor surface of the image sensor, a pixelcorresponds, for example, to a square area, within which a respectiveincoupling area lies. By way of example, the incoupling area can form afraction of the pixel area.

In the case of a pixel edge length of 100 μm and N2=4096 incouplingareas, the image sensor can have, e.g., 64×64 pixels which could bearranged in a square matrix, as a result of which the image sensor has asensor surface of 6.4×6.4 mm²=40.96 mm².

According to a second aspect, a position sensor apparatus forascertaining a position of at least one mirror of a lithographyapparatus is proposed. The position sensor apparatus includes a patternprovision device, coupled to the mirror, for providing a pattern whichhas information content at spatial frequencies of at least 1/(500 μm),an image sensor for capturing the provided pattern and for providing areconstructed image of the captured pattern, and an image evaluationdevice for ascertaining the position of the mirror on the basis of thereconstructed image. The image sensor corresponds to the image sensor ofthe first aspect or of one of the embodiments.

The present position sensor apparatus can capture an image of theprovided pattern and hence also can be referred to as an image-basedposition sensor apparatus or an image-based position sensor.

By using the pattern with information content at spatial frequencies ofat least 1/(500 μm), the present position sensor apparatus can be ableto provide high measurement accuracy. Here, the spatial frequencies ofat least 1/(500 μm) cam determine a minimum accuracy of the positiondetermination ensured by the present position sensor apparatus. Even ifthe pattern contains spatial frequencies of only to 1/(500 μm),measurement accuracies that are much more accurate than 1 μm arepossible.

By way of the image-based position sensor apparatus, it is possible toalso capture parasitic effects, such as scaling or tilting of thepattern provision device relative to the image sensor, and alsocompensate these. The image sensor can provide the reconstructed image,in particular as a digital image of the provided pattern. In particular,the digital image can be embodied as an electrical signal or as anelectrical signal sequence which contains information about the mirror'sposition or represents the latter.

In particular, the light signals that represent the pattern can beinitially supplied internally by the image sensor in purely opticalfashion to the image reconstruction apparatus, and the light signals areonly digitized by the latter. As a result of the spatially separatedsignal capture and digitization of the light signals, a great degree offlexibility can be provided in relation to an arrangement and acomputing capacity of the image reconstruction apparatus.

In particular, a pattern should be understood to mean a processedsurface, wherein the processed surface has information content atspatial frequencies of at least 1/(500 μm). By way of example, theprocessed surface can be a metal-processed surface or a printed surface.By way of example, the metal-processed surface can be produced bymilling or grinding. By way of example, the material of the pattern canbe metal, silicon or glass. By way of example, the pattern can also beembodied as a metal-processed surface of a carrier structure of themirror. The structuring of the surface of the carrier structure andhence the information content of the pattern can be formed, for example,by milling or grinding the carrier structure. By way of example, thepattern can also be a pattern produced by lithography.

In particular, the image evaluation device can integrated in a digitalcircuit or digital component. By way of example, the image evaluationdevice can be part of the image reconstruction apparatus.

An integrated component should be understood to mean an arrangementhaving a number of integrated circuits and/or parts that are arranged ona carrier printed circuit board or on a plurality of carrier printedcircuit boards. The integrated component could also be referred to asintegrated sensor electronics.

In the present case, an “integrated circuit” should be understood tomean an electronic circuit (also referred to as monolithic circuit)arranged on a single semiconductor substrate (wafer).

By way of example, the digital circuit can be a programmable digitalcircuit (field-programmable gate array, FPGA) or an application-specificdigital circuit (application-specific integrated circuit, ASIC).

According to a third aspect, a lithography apparatus with a projectionsystem with at least one mirror including the position sensor apparatusas per the second aspect is proposed.

In particular, the lithography apparatus can be an EUV or DUVlithography arrangement. EUV stands for “extreme ultraviolet” and refersto a wavelength of the working light of between 0.1 and 30 nm. DUVstands for “deep ultraviolet” and refers to a wavelength of the workinglight of between 30 and 250 nm.

According to a fourth aspect, a method for operating an image sensor, inparticular an image sensor as per the first aspect, is proposed. In afirst step, light, incident on an incoupling area of a plurality N2 ofincoupling areas, is coupled into an assigned integrated opticalwaveguide of a plurality N1 of integrated optical waveguides. In asecond step, a light signal is generated in the assigned integratedoptical waveguide of the plurality N1 of integrated optical waveguides.In a third step, the plurality N1 of integrated optical waveguides arecoupled to a multiplexer apparatus. In a fourth step, the light signals,generated in the N1 integrated optical waveguides, are multiplexed to anumber N3 of secondary optical waveguides via the multiplexer apparatus.In a fifth step, the N3 secondary optical waveguides are coupled to animage reconstruction apparatus and, in a sixth step, an image isreconstructed on the basis of the light signals of the N3 secondaryoptical waveguides via the image reconstruction apparatus.

This method allows advantageous operation of an image sensor, in whichthe image capture in the form of light signals and the conversion of thecaptured light signals into electrical signals occur spatially separatedfrom one another.

Furthermore, a computer program product is proposed, the computerprogram product causing the method as explained above to be carried outon a program-controlled device.

A computer program product, such as e.g. a computer program product, canbe provided or supplied, for example, as a storage medium, such as e.g.a memory card, a USB stick, a CD-ROM, a DVD, or else in the form of adownloadable file from a server in a network. By way of example, in awireless communications network, this can be effected by transferring anappropriate file with the computer program product or the computerprogram product.

The embodiments and features described for the proposed image sensor canbe correspondingly applicable to the proposed method.

Further possible implementations of the disclosure also include notexplicitly mentioned combinations of features or embodiments describedabove or below with respect to the exemplary embodiments. In this case,a person skilled in the art will also add individual aspects asimprovements or supplementations to the respective basic form of thedisclosure.

Further configurations and aspects of the disclosure are the subjectmatter of the dependent claims and also of the exemplary embodiments ofthe disclosure described below.

BRIEF DESCRIPTION OF THE DRAWINGS

In the text that follows, the disclosure is explained in more detail onthe basis of exemplary embodiments and with reference to theaccompanying figures.

FIG. 1 shows a schematic view of an EUV lithography apparatus;

FIG. 2 shows a schematic view of a cross section of a first exemplaryembodiment of an image sensor;

FIG. 3 shows a schematic view of a cross section of a second exemplaryembodiment of an image sensor;

FIG. 4 shows a schematic view of a cross section of a third exemplaryembodiment of an image sensor;

FIG. 5 shows a schematic view of a cross section of a fourth exemplaryembodiment of an image sensor;

FIG. 6 shows a schematic detailed view of a cross section of a fifthexemplary embodiment of an image sensor;

FIG. 7 shows a schematic view of a cross section of a sixth exemplaryembodiment of an image sensor;

FIG. 8 shows a schematic view of a cross section of a seventh exemplaryembodiment of an image sensor;

FIG. 9 shows a schematic view of an exemplary embodiment of a positionsensor apparatus;

FIG. 10 shows a plan view of an exemplary embodiment of an integratedoptical image sensor; and

FIG. 11 shows a block diagram of an exemplary embodiment of a method foroperating an image sensor.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

Identical elements or elements having an identical function have beenprovided with the same reference signs in the figures, unless indicatedotherwise. Further, the illustrations in the figures are not necessarilytrue to scale.

FIG. 1 shows a schematic view of an EUV lithography apparatus 100A,which includes a beam-shaping and illumination system 102 and aprojection system 104. EUV stands for “extreme ultraviolet” and refersto a wavelength of the working light of between 0.1 and 30 nm. Thebeam-shaping and illumination system 102 and the projection system 104are respectively provided in a vacuum housing, each vacuum housing beingevacuated using an evacuation apparatus that is not depicted morespecifically. The vacuum housings are surrounded by a machine room notillustrated in any more detail, in which, e.g., electrical controllersand the like are provided.

The EUV lithography apparatus 100A includes an EUV light source 106A. Aplasma source which emits radiation 108A in the EUV range (extremeultraviolet range), i.e., for example, in the wavelength range of 5 nmto 30 nm, may be provided, for example, as the EUV light source 106A. Inthe beam shaping and illumination system 102, the EUV radiation 108A isfocused and the desired operating wavelength is filtered out from theEUV radiation 108A. The EUV radiation 108A generated by the EUV lightsource 106A has a relatively low transmissivity through air, for whichreason the beam guiding spaces in the beam shaping and illuminationsystem 102 and in the projection system 104 are evacuated.

The beam shaping and illumination system 102 depicted in FIG. 1 has fivemirrors 110, 112, 114, 116, 118. After passing through the beam shapingand illumination system 102, the EUV radiation 108A is guided onto thephotomask (reticle) 120. The photomask 120 is likewise embodied as areflective optical element and can be arranged outside the systems 102,104. Furthermore, the EUV radiation 108A may be steered onto thephotomask via a mirror 122. The photomask 120 has a structure which isimaged onto a wafer 124 or the like in a reduced fashion by viaprojection system 104.

The projection system 104 has six mirrors M1-M6 for imaging thephotomask 120 onto the wafer 124. In this case, individual mirrors M1-M6of the projection system 104 can be arranged symmetrically in relationto the optical axis 126 of the projection system 104. It should be notedthat the number of mirrors of the EUV lithography apparatus 100A is notrestricted to the number illustrated.

More or fewer mirrors could also be provided. Furthermore, the mirrorsM1-M6 are generally curved on their front side for beam shaping.

The projection system 104 further has a number of position sensorapparatuses 140 for determining a position of one of the mirrors M1-M6.Without loss of generality and for reasons of simplified illustration,FIG. 1 shows one position sensor apparatus 140. The shown positionsensor apparatus 140 includes an internal group 150, which is arrangedin the evacuated housing of the projection system 104, and an externalgroup 170, which is arranged outside of the housing, a signal connection160 transferring signals, in particular optical and electrical signals,between the internal group 150 and the external group 170.

The internal group 150 of the position sensor apparatus 140 includes, inparticular, a pattern provision device 142, coupled to the respectivemirror M1-M6, and a sensor front end 270, which has a substrate 202 withan integrated optical circuit (see FIGS. 2-8), for example.

The signal connection 160 includes, in particular, a number N3 ofsecondary optical waveguides 240 (see FIGS. 2-10), a number N4 ofillumination optical waveguides 292 (see FIG. 7, 9 or 10), and at leastone electrical signal cable for transferring a synchronization signal260 (see FIG. 6, 7, 9 or 10).

The external group 170 of the position sensor apparatus 140 includes, inparticular, an image reconstruction apparatus 250 (see FIGS. 2-9), animage evaluation device 146 (see FIG. 9), and, optionally, anillumination device 290 (see FIG. 7 or 9).

Should a plurality of position sensor apparatuses 140 be provided,provision can advantageously be made for a plurality of internal groups150 to be coupled via a respective signal connection 160 to a smallerplurality of external groups 170. In particular, should a determinationof the position in six axes be desired for one mirror M1-M6, involving,e.g., six of the internal groups 150, only one external group 170 canadopt the capture and evaluation of the image signals for these sixinternal groups 150. Consequently, this external group 170 suppliescomplete position information in six axes for the monitored mirrorM1-M6.

FIG. 2 shows a schematic view of a cross section of a first exemplaryembodiment of an image sensor 200, which can find use, for example, inthe position sensor apparatus 140 of FIG. 1. The image sensor 200includes a sensor front end 270 with a substrate 202 with a plurality ofintegrated optical elements 210, 220 230, and also a secondary opticalwaveguide 240 and an image reconstruction apparatus 250.

In this example, the substrate 202 has N2=4 incoupling areas 210, whichare configured to couple light incident thereon into the respective oneof the N1=4 integrated optical waveguides 220 such that a light signalis generated in the latter. The four integrated optical waveguides 220guide the light signals to an integrated optical multiplexer apparatus230 which is arranged on the same substrate 202. In this view, the fourintegrated optical waveguides 220 are disposed in layers of thesubstrate 202 at different depths. However, this only serves to clarifythe illustration. In an actual substrate 202, the N1 integrated opticalwaveguides can be arranged next to one another in the same layer and/orabove one another in different layers.

The multiplexer apparatus 230 is configured to multiplex the lightsignals supplied thereto to a secondary optical waveguide 240 coupledtherewith. In this exemplary embodiment, this is a 4×1 multiplexerapparatus 230. By way of example, the secondary optical waveguide 240 isembodied as a glass fiber with a length of 10 m. The glass fiber 240transmits the light signal input coupled by the multiplexer apparatus230 to the image reconstruction apparatus 250.

The image reconstruction apparatus 250 captures the supplied lightsignal and reconstructs an image on the basis of the light signal. Inparticular, the reconstructed image corresponds to an image present on asurface of the substrate 202. By way of example, details of the imagereconstruction apparatus 250 are illustrated in FIG. 6.

FIG. 3 shows a schematic view of a cross section of a second exemplaryembodiment of an image sensor 200, which can find use, for example, inthe position sensor apparatus 140 of FIG. 1. Deviating from the firstexemplary embodiment (see FIG. 2), the second exemplary embodiment hasan integrated optical multiplexer apparatus 230 with two stages 232,234; otherwise, it is identical. By using a plurality of multiplexerstages 232, 234, it is possible, for example, to reduce the complexityof a structure of the multiplexer apparatus 230.

FIG. 4 shows a schematic view of a cross section of a third exemplaryembodiment of an image sensor 200, which can find use, for example, inthe position sensor apparatus 140 of FIG. 1. The third exemplaryembodiment differs from the first exemplary embodiment (see FIG. 2) inthat the plurality N1=2 of integrated optical waveguides 220 is reduced.In this case, each of the two integrated optical waveguides 220 has twoincoupling areas 210 assigned thereto (N2=4), with light signalsgenerated in the integrated optical waveguide 220 by the respectiveincoupling areas 210 being merged at a junction 222 in the integratedoptical waveguide 220. Hence, each of the integrated optical waveguides220 in this example transmits two light signals. By way of example, thelight signals can differ in terms of their polarization or frequency, asa result of which they can be discriminated by way of an appropriatefilter. The further properties of the image sensor 200 are identical tothe first exemplary embodiment.

FIG. 5 shows a schematic view of a cross section of a fourth exemplaryembodiment of an image sensor 200, which can find use, for example, inthe position sensor apparatus 140 of FIG. 1. In contrast to the firstexemplary embodiment (see FIG. 2), two secondary optical waveguides 240are provided in this case. Accordingly, the illustrated multiplexerapparatus 230 is embodied as a 4×2 multiplexer. The image reconstructionapparatus 250 is accordingly configured to capture the light signalsfrom the two secondary optical waveguides 240 and reconstruct the imageon the basis of the captured light signals. The further detailscorrespond to those of the first exemplary embodiment.

FIG. 6 shows a schematic view of a cross section of a fifth exemplaryembodiment of an image sensor 200, which can find use, for example, inthe position sensor apparatus 140 of FIG. 1. In this sixth exemplaryembodiment, the image reconstruction apparatus 250, in particular, isshown in detail. For the sake of clarity, the details of the sensorfront end 270 were not illustrated (in this respect, see, e.g., FIG.2-5, 7, 8 or 10).

Accordingly, the image reconstruction apparatus 250 has a capturingdevice 252, which is embodied as a photodiode here and which isconfigured to capture the light signals supplied by the secondaryoptical waveguide 240 and convert these into an electrical signal. Theelectrical signal generated by the photodiode 252 correlates with abrightness or intensity of a respective light signal, in particular. Theelectrical signal generated by the photodiode 252 is supplied to ananalog-to-digital converter 256 (A/D converter). Further, provision canbe made for the electrical signal of the photodiode 252 to be suppliedto an amplifier (not illustrated), which amplifies the electrical signaland outputs the amplified signal to the A/D converter 256. The A/Dconverter 256 converts the electrical signal into a digital data signal.The digital data signal is a 12-bit bit string, for example, whichincludes brightness information. Consequently, 4096 brightness levelsare distinguishable using this digital data signal. Thus, a singledigital data signal includes an information item that depends on thelight incident on the corresponding incoupling area 210. The digitaldata signal is output to an image processor 258. From a plurality of N2received digital data signals, the image processor 258 reconstructs animage with N2 pixels, which corresponds in terms of the informationcontent to the image on the sensor surface of the sensor front end 270.

Furthermore, the image reconstruction apparatus 250 includes asynchronization device 254. The synchronization device 254 is embodiedas a clock and provides a synchronization signal 260. Thissynchronization signal 260, or a synchronization signal derivedtherefrom, is firstly transferred to the multiplexer apparatus 230 viaan electrical signal line and secondly also transferred to the A/Dconverter 256 and the image processor 258. The synchronization signal260 serves to synchronize the multiplexer apparatus 230, the A/Dconverter 256, and the image processor 258. The synchronization device254 interacts with the multiplexer apparatus 230, the A/D converter 256,and the image processor 258 in such a way that a unique assignment of alight signal captured by the capturing device 252 to one of the N2incoupling areas 210 is ensured. This allows every digital data signalto be uniquely assigned to the correct pixel for the reconstructedimage.

FIG. 7 shows a schematic view of a cross section of a sixth exemplaryembodiment of an image sensor 200, which can find use, for example, inthe position sensor apparatus 140 of FIG. 1. In particular, this sixthexemplary embodiment has the features of the first exemplary embodiment(see FIG. 2) and of the fifth exemplary embodiment (see FIG. 6), withthe details of the image reconstruction apparatus 250 not beingillustrated here for reasons of clarity. Further, the reference signsfor the incoupling areas 210 and the integrated optical waveguides 220were dispensed with for reasons of clarity (see, e.g., FIG. 2).

The sixth exemplary embodiment of the image sensor 200 is additionallyconfigured to provide light for illumination purposes, for example forilluminating a pattern 144 (see, e.g., FIG. 8 or FIG. 9). To this end,the sensor front end 270 includes additional integrated opticalstructures. In particular, the substrate 202 has N4=3 secondaryintegrated optical waveguides 282, which are configured to guide a lightsignal to N5=3 outcoupling areas 284 arranged on a surface of thesubstrate 202. The light signal can emerge from the three secondaryintegrated optical waveguides 282 via the three outcoupling areas 284.Further, provision is made of an integrated optical distributionapparatus 280, which distributes an externally supplied light signalamong the three secondary integrated optical waveguides 282.

An illumination device 290, which is embodied as a laser diode, forexample, is provided to generate the light signal. Initially, the laserdiode 290 generates a light signal in an illumination optical waveguide292, which is embodied as a glass fiber, for example. By way of example,the glass fiber 292 can have a length of more than 10 m. Hence, thelaser diode 290 is flexibly arrangeable, in particular at a locationwhere efficient cooling is easily realizable. As an alternative or inaddition to a laser diode, provision can be made of a furtherillumination device 290, for example an arc lamp or any other lightsource (not illustrated). Further, a glass fiber bundle can be providedinstead of a glass fiber (not illustrated).

The glass fiber 292 is coupled to the distribution apparatus 280. Inthis example, the distribution apparatus 280, as a passive integratedoptical structure, is arranged on the same substrate 202 as the furtherintegrated optical structures of the sensor front end 270 of the imagesensor 200. The distribution apparatus 280 distributes the light signalinput coupled by the glass fiber 292 among the three secondaryintegrated optical waveguides 282, which guide the light signal to thethree outcoupling areas 284, which allow the light signal to leave thesecondary integrated optical waveguides 282.

This sixth exemplary embodiment in FIG. 7 shows three secondaryintegrated optical waveguides 282 and three outcoupling areas 284.Deviating herefrom, more or fewer secondary integrated opticalwaveguides 282 and/or outcoupling areas 284 could also be provided.Further, a deviating arrangement of the outcoupling areas 284, inparticular, could be provided, for example only at the edge of thesubstrate 202. Provision can also be made for the distribution apparatus280, the secondary integrated optical waveguides 282, and theoutcoupling areas 284 to be arranged on a dedicated substrate 202, i.e.,separately from the incoupling areas 210, integrated optical waveguides220, and/or the multiplexer apparatus 230. In this case, the sensorfront end 270 would include two substrates 202 (not illustrated).

FIG. 8 shows a schematic view of a cross section of a seventh exemplaryembodiment of an image sensor 200, which can find use, for example, inthe position sensor apparatus 140 of FIG. 1. The image sensor 200 in theseventh exemplary embodiment includes a substrate 202 with fourincoupling areas 210 and four integrated optical waveguides 220. In thisexemplary embodiment, the multiplexer apparatus 230 is arranged on aseparate integrated optical component, which is arranged next to thesubstrate 202 in such a way that it can multiplex light signals from theintegrated optical waveguides 220 to the secondary optical waveguide240. The multiplexer apparatus 230 is embodied as a 4×1 multiplexer. Theimage reconstruction apparatus 250 is configured to reconstruct an imageon the basis of the light signals supplied by the secondary opticalwaveguide 240.

In particular, the image sensor 200 in this exemplary embodimentincludes an imaging apparatus 204, which is arranged spatially upstreamof the substrate 202 on the side of the incoupling areas 210. Theimaging apparatus 204 is embodied as a micro-optical unit, which isconfigured to image an object point to be imaged, of the pattern 144 inthe present case, on an incoupling area 210. This is indicated by thelight beams 148 drawn using dashed lines. Accordingly, the micro-opticalunit 204 generates an image representation of the pattern 144 on thesensor surface on which the incoupling areas 210 are arranged.

Consequently, the sensor front end 270 in this exemplary embodimentincludes the micro-optical unit 204, the substrate 202 with theincoupling areas 210 and integrated optical waveguides 220, and themultiplexer apparatus 230.

In addition to the image sensor 200, FIG. 8 also shows a patternprovision device 142, which provides the pattern 144. In particular, thepattern 144 has information content at predetermined spatialfrequencies, which allows determination of a relative displacement ofthe pattern 144 from a reference position, for example an informationcontent at 1/(500 μm). Both the desired information content of thepattern 144 and the desired resolution of the image sensor 200 depend,in particular, on the desired accuracy of the determination of such arelative displacement. In particular, the resolution of the image sensor200 corresponds to the plurality N2 of incoupling areas 210.

FIG. 9 shows a schematic view of an exemplary embodiment of a positionsensor apparatus 140, which can be used, for example, for ascertaining aposition of a mirror M1-M6 of an EUV lithography apparatus 100A, asillustrated in FIG. 1. The position sensor apparatus 140 includes theinternal group 150, likewise illustrated in FIG. 1, the external group170, and the signal connection 160.

Firstly, the internal group 150 includes the pattern provision device142 with the pattern 144, which is arranged at a mirror M1, which ispart of a projection system 104 of the EUV lithography apparatus 100A(see FIG. 1), for example, and the position of which should be monitoredor determined in the present case. Additionally, the internal group 150includes the sensor front end 270. No details of the sensor front end270 have been illustrated here for reasons of clarity. In particular,the sensor front end 270 can be embodied like in one of the exemplaryembodiments illustrated in FIGS. 2-8.

FIG. 10 shows a plan view of an exemplary embodiment of a sensor frontend 270, which is integrated in a single substrate 202 in the presentcase. By way of example, the illustrated exemplary embodiment is usablein a position sensor apparatus 140 of FIG. 1 or 9.

This exemplary embodiment only illustrates the components/functionalunits arranged on the surface of the substrate 202; the functional unitsburied in a lower layer in the substrate 202 have not been shown. Thelatter are, in particular, integrated optical waveguides 220 (see FIGS.2-8), secondary integrated optical waveguides 282 (see FIG. 7), andelectronic signal connections.

In the illustrated exemplary embodiment, N2=16 incoupling areas 210,which are arranged in a rectangular 4×4 matrix arrangement, are arrangedon the surface. Only one of the incoupling areas 210 has been labeled bya reference sign in order to keep the illustration clear. Furthermore,N5=4 outcoupling areas 284 are arranged between the incoupling areas210. Again, only one of the outcoupling areas 284 is labeled by areference sign. A multiplexer apparatus 230 is arranged on theright-hand side of the substrate 202 in the drawing; it is coupled to asecondary optical waveguide 240. Each of the incoupling areas 210 isconfigured to generate a light signal in an integrated optical waveguide220 (not illustrated) to which it is assigned. The integrated opticalwaveguides 220 guide the light signals to the multiplexer apparatus 230,which transmits the latter in accordance with a specified multiplexingmethod to the secondary optical waveguide 240. A distribution apparatus280 is disposed below the multiplexer apparatus 230 in the drawing,likewise on the right-hand side of the substrate 202. The distributionapparatus is coupled to an illumination optical waveguide 292. By way ofexample, the illumination optical waveguide 292 guides a monochromaticlight signal, which is generated by an illumination apparatus 290 (see,e.g., FIG. 7 or 9), not illustrated here, e.g., a laser source, to thedistribution apparatus 280. The distribution apparatus 280 distributesthe light signal among a number N4 of secondary integrated opticalwaveguides 282 (not illustrated), which supply the light signal to thefour outcoupling areas 284, by which the light signal can be outputcoupled from the secondary integrated optical waveguides 282.

A total of five contact points 262, which are supplied with thesynchronization signal 260, for example, by way of a signal line, arearranged on the left-hand side of the substrate 202 in the drawing. Thecontact points 262 are connected to the multiplexer apparatus 230 forthe purposes of driving the latter via electrical signal lines, notillustrated here, which are integrated in the substrate 202. Anindividual control signal can be supplied to each of the contact points262 via the synchronization signal 260. As an alternative to thisillustration, provision can be made for the contact points 262 to bearranged on the back side of the substrate 202.

FIG. 11 shows a block diagram of an exemplary embodiment of a method foroperating an image sensor 200, for example the image sensor 200 of oneof the exemplary embodiments in FIGS. 2-8.

In a first method step S1, light is coupled from an incoupling area 210into an integrated optical waveguide 220. In a second method step S2, alight signal is generated in the assigned integrated optical waveguide220. In a third method step, the plurality N1 of integrated opticalwaveguides 220 are coupled to a multiplexer apparatus 230. Themultiplexer apparatus 230 is configured to multiplex the light signalsto a number N3 of secondary optical waveguides 240 in a fourth methodstep S4. In a fifth method step S5, the number N3 of secondary opticalwaveguides 240 are coupled to an image reconstruction apparatus 250. Theimage reconstruction apparatus 250 captures the light signals andreconstructs an image on the basis of the captured light signals in asixth method step S6.

Although the present disclosure has been described on the basis ofexemplary embodiments, it is modifiable in diverse ways.

LIST OF REFERENCE SIGNS

-   100 Lithography apparatus-   100A EUV lithography apparatus-   102 Beam shaping and illumination system-   104 Projection system-   106A EUV light source-   108A EUV radiation-   110 Mirror-   112 Mirror-   114 Mirror-   116 Mirror-   118 Mirror-   120 Photomask-   122 Mirror-   124 Wafer-   126 Optical axis of the projection system-   136 Mirror-   137 Vacuum housing-   140 Position sensor apparatus-   142 Pattern provision device-   144 Pattern-   146 Image evaluation device-   148 Light beams-   150 Internal group-   160 Signal connection-   170 External group-   200 Image sensor-   202 Substrate-   204 Imaging unit-   210 Incoupling area-   220 Integrated optical waveguide-   230 Multiplexer apparatus-   232 Multiplexer stage-   234 Multiplexer stage-   240 Secondary optical waveguide-   250 Image reconstruction apparatus-   252 Capturing device-   254 Synchronization device-   256 Analog-to-digital converter-   258 Image processor-   260 Synchronization signal-   262 Contact point-   270 Sensor front end-   280 Distribution apparatus-   282 Secondary integrated optical waveguide-   284 Outcoupling area-   290 Illumination device-   292 Illumination optical waveguide-   M1 Mirror-   M2 Mirror-   M3 Mirror-   M4 Mirror-   M5 Mirror-   M6 Mirror-   S1 Method step-   S2 Method step-   S3 Method step-   S4 Method step-   S5 Method step-   S6 Method step

What is claimed is:
 1. An image sensor, comprising: a plurality N1 ofintegrated optical waveguides; a plurality N2 of incoupling areas; amultiplexer apparatus; and an image reconstruction apparatus, wherein:N2≥N1; each of the N2 incoupling areas is assigned to one of the N1integrated optical waveguides; each of the N2 incoupling areas isconfigured to couple incident light into its assigned integrated opticalwaveguide so a light signal is generated in the assigned integratedoptical waveguide; the multiplexer apparatus is coupled to the N1integrated optical waveguides to multiplex the light signals generatedin the N1 integrated optical waveguides to a number N3 of secondaryoptical waveguides; N1≥N3, and the image reconstruction apparatus iscoupled to the N3 secondary optical waveguides to reconstruct an imageon the basis of the light signals of the N3 secondary opticalwaveguides.
 2. The image sensor of claim 1, wherein the plurality N2 ofincoupling areas, the plurality N1 of integrated optical waveguides, andthe multiplexer apparatus are integrated on a substrate.
 3. The imagesensor of claim 1, wherein the multiplexer apparatus is configured tomultiplex the light signals via at least one method selected from thegroup consisting of a time-division multiplexing method, afrequency-division multiplexing method, and a code-division multiplexingmethod.
 4. The image sensor of claim 1, wherein the image reconstructionapparatus further comprises: a capturing device configured to capturethe light signals of the N3 secondary optical waveguides; and asynchronization device configured to drive the multiplexer apparatus viaa synchronization signal so that a respective light signal captured bythe capturing device is uniquely assignable to an incoupling area of theplurality N2 of incoupling areas of the image sensor.
 5. The imagesensor of claim 1, wherein a surface of a respective incoupling area ofthe plurality N2 of incoupling areas has a predetermined angle withrespect to the incident light.
 6. The image sensor of claim 1, furthercomprising an imaging unit configured to image a pattern a patternprovision device, to be captured by the image sensor, on the pluralityN2 of incoupling areas of the image sensor.
 7. The image sensor of claim1, wherein: the image sensor comprises a number N4 of secondaryintegrated optical waveguides and a number N5 of outcoupling areas;N5≥N4; each of the N5 outcoupling areas is assigned to one of the N4secondary integrated optical waveguides; and each of the N5 outcouplingareas is configured to output couple from the assigned secondaryintegrated optical waveguide a light signal, generated in the assignedsecondary integrated optical waveguide, to illuminate a pattern of apattern provision device to be captured by the image sensor.
 8. Theimage sensor of claim 7, further comprising an illumination deviceconfigured to generate a light signal in an illumination opticalwaveguide and a distribution apparatus coupled to the illuminationoptical waveguide to distribute the light signal generated in theillumination optical waveguide among the number N4 of secondaryintegrated optical waveguides.
 9. The image sensor of claim 7, whereinat least two members selected from the group consisting of the number N4of secondary integrated optical waveguides, the number N5 of outcouplingareas, and the distribution apparatus are integrated on the substrate.10. The image sensor of claim 7, wherein the plurality N2 of incouplingareas, the plurality N1 of integrated optical waveguides, and themultiplexer apparatus are integrated on a substrate.
 11. The imagesensor of claim 1, wherein 16≤N2≤16384.
 12. The image sensor of claim 1,wherein a structure dimension of at least one member selected from thegroup consisting of the N1 integrated optical waveguides and the N4secondary integrated optical waveguides is less than 100 μM.
 13. Theimage sensor of claim 1, wherein an edge length of a pixel of the imagesensor lies in the range between 5 μm and 1 mm.
 14. The image sensor ofclaim 1, wherein the image sensor is configured to be used in a positionsensor apparatus to ascertain a position of at least one mirror of alithography apparatus.
 15. A position sensor apparatus, comprising: apattern provision device configured to be coupled to a mirror of alithography apparatus and configured to provide a pattern comprisinginformation content at spatial frequencies of at least 1/(500 μm); animage sensor according to claim 1, the image sensor configured tocapture the pattern and to provide a reconstructed image of the capturedpattern; and an image evaluation device configured to ascertain theposition of the mirror on the basis of the reconstructed image.
 16. Alithography apparatus, comprising: a projection system comprising amirror; and a position sensor apparatus, comprising: a pattern provisiondevice configured to be coupled to a mirror of a lithography apparatusand configured to provide a pattern comprising information content atspatial frequencies of at least 1/(500 μm); an image sensor according toclaim 1, the image sensor configured to capture the pattern and toprovide a reconstructed image of the captured pattern; and an imageevaluation device configured to ascertain the position of the mirror onthe basis of the reconstructed image.
 17. The apparatus of claim 16,further comprising an illumination system.
 18. The apparatus of claim17, further comprising an EUV light source.
 19. A method of using alithography apparatus comprising an illumination system and a projectionsystem, the method comprising: using the illumination system toilluminate a mask comprising a structure; and using the projectionsystem to project the illuminated structure onto a substrate, whereinthe lithography apparatus comprises an image sensor according toclaim
 1. 20. A method of operating an image sensor for a position sensorapparatus for ascertaining a position of a mirror of a lithographyapparatus, the method comprising: coupling light, incident on anincoupling area of a plurality N2 of incoupling areas, into an assignedintegrated optical waveguide of a plurality N1 of integrated opticalwaveguides; generating a light signal in the assigned integrated opticalwaveguide of the plurality N1 of integrated optical waveguides; couplingthe plurality N1 of integrated optical waveguides with a multiplexerapparatus; multiplexing the light signals, generated in the N1integrated optical waveguides, to a number N3 of secondary opticalwaveguides via the multiplexer apparatus; coupling the N3 secondaryoptical waveguides with an image reconstruction apparatus; andreconstructing an image on the basis of the light signals of the N3secondary optical waveguides via of the image reconstruction apparatus.